The use of the occlusogram in planning orthodontic treatnaent Michael
R. Marcotte,
Famingto?t,
D.D.S.,
M.S.D.*
Conw
P
articularlp since the advent of radiographic cephalometrics, orthodontists have planned treatment primarily in two dimensions, although earlier leaders in the field, such as Simon1 developed three-dimensional analytical procedures. Currently, the lateral cephalometric head film is used in many respects, to the exclusion of records that define the third dimension, Methods for producing positive-print 1 :l photographs of dental casts were earlier developed by C. J. Burstone ; with tracings of these photographs (occlusograms) and proper cephalometric head films, it is now possible to make treatment discussions in all three planes of space.2 It is the purpose of this article to demonstrate the use of the occlusogram in planning orthodontic treatment and to describe the procedures in sufficient detail so that it can be used practically. Specifically, the procedures will permit the orthodontist to determine (1) the anchorage requirements, (2) the arch length status, (3) the final arch widths, (4) the teeth to be removed, if any, and (5) the final occlusal relationships. Occlusogram
procedure
The records of Patient I). B., a Caucasian girl with a developmental age of 11 years 6 months, will be used to illustrate the procedures. The occlusogram procedure requires accurate positive-print photographs of the occlusal aspects of oriented dental casts. The dental impressions are made in the usual manner, and the resulting casts must be trimmed according to the following specifications : The posterior borders of the dental casts are trimmed perpendicular to the occlusal plane (Fig. 1). Since the centric relation position of the dental casts will be used as a reference position, the posterior borders of the casts must be made flush with each other when the casts are in the. centric relation position. This reference position requires that the wax jaw registration be made with the mandible in *Assistant Medicine.
Professor
of
Orthodontics,
University
of
Connecticut
School
of
Dental
655
656
Fig.
Awl.
Maqrcotte
1. The
posterior
borders
Fig.
2.
Fig.
3. The
Registration
Fig.
4. A 1: 1 positive-print
occlusogram
of the
grooves
are
camera film
dental
casts
placed
assembly of the
in for
occlusal
are the
perpendicular posterior
producing aspects
to the surfaces
occlusal of
1 :l positive-print of the dental
the
J. Orthod. June 1976
plane. dental
casts.
films. casts.
its most retruded position and that the wax registration recording the occlusal surfaces of the teeth be made without perforating the wax. This wax centric relation registration is then placed between the dental casts while the posterior borders of the casts are trimmed. Viewed from the occlusal aspect, the posterior borders of the casts are also perpendicular to the palatal midline and, for lateral orientation, each cast will have an extended registration groove (Fig. 2). This registration groove is placed in the backs of both casts simultaneously by means of a custom-made dental cast scriber. The casts have thus been trimmed with their backs mutually perpendicular to the occlusal plane and to the palatal midline and have also been scribed to permit the positive-print occlusograms to be oriented laterally. The casts are then finished and polished in the usual manner.
0cclusogra.m
in treatment
planning
6S7
To make standard photographs of the occlusal aspects of the dental casts, the occlusogram camera assembly consists of a 4 by 5 inch box camera, a dental cast stage, two 375watt floodlights, and a hinged Plexiglas plate (Fig. 3). The camera is mounted on a sliding track, so that the distance from the edge of the stage can be adjusted and fixed to produce a 1 :l magnification. For this particular installation, a 210 mm. lens is found to be satisfactory. The dental cast stage has an adjustable guide onto which fit the registration grooves on the backs of the dental casts. Each dental cast is placed on this stage guide and is brought up to the leading edge of the stage. Since the camera has been focused on this leading edge, the occlusal aspects of the dental cast are in focus at a 1 :l magnification. Registration dots which are located in the leading edge of the stage will also be recorded on the occlusogram. With a fine-grain positive film placed into the film cassette, and with both floodlights focused on the dental cast, a typical exposure of 4 seconds at f45 is made. Processed according to manufacturer’s directions, maxillary and mandibular occlusograms are produced at 1 :l magnification (Fig. 4). Using the registration dots on the leading edge of the stage as reference points, both occlusograms are registered on these dots and permanently fixed at the bottom edge with a noncracking type of tape (for example, Mylar tape). Since the positive-print film is transparent, the existing occlusal relationships in centric relation can be seen when the occlusograms are folded over. For most treatment procedures, however, an occlusogram tracing is required. For this occlusogram tracing, acetate paper is placed over the occlusograms and the maxillary and mandibular teeth are outlined, showing the gingival tooth contours, incisal edges, buccal cusp ridges, central grooves, and cusp tips. Also traced are the palatal rugae, the midpalatal raphe, the fovea palatinus, and the registration dots (Fig. 5). Application
to orthodontic
treatment
planning
In order to orient the occlusogram tracings, midsagittal and transverse‘registration lines are constructed. The maxillary midsaggittal registration line is constructed by connecting the midpoints of the incisive papilla, the midpalatal raphe, and the fovea palatinus (Fig. 6). The maxillary transverse registration line is constructed distal to the last molar in the arch and perpendicular to the midsagittal registration line. The maxillary and mandibular occlusogram tracings are then separated by cutting the acetate paper midway between both tracings. The occlusogram tracings are assembled, using the registration dots, and the maxillary registration lines are duplicated on the mandibular occlusogram tracing (Fig. 7). Both pieces of tracing paper, when oriented as in Fig. 7, can be thought of as the maxillary and mandibular denture bases in centric relation at the beginning of orthodontic treatment. Since the anteroposterior position of the denture bases is influenced by growth, facial growth rotations, changes in the cant of the occlusal plane, and/or surgery, these positions should be anticipated for the period of treatment and incorporated into the occlusogram tracings.
AWL J. Orthod. June 1976
. .
I
*-
D.8 11.6 ~WWS-solid line 13.6 years--dashed lme Net change
in A- Pg (OP):2,9m
Denrcfoctal Trerxtmmt Obtecrivan--dotted line
Fig.
5. Occlusogram
Fig. 6. The maxillary raphe, and the fovea Fig. 7. Both registration Fig.
tracing. midsagittal palatinus.
occlusogram tracings lines are transferred
8. Dentofacial
objectives
line
connecting
are assembled to the mandibular
diagrammed
the
incisive
papilla,
on the registration dots, occlusogram tracing.
on a 2-year
growth
estimate.
the and
midpalatal the
maxillary
From the initial tracing of Patient I). B.‘s cephalometric head film, a. “-year growth estimate is made with the teeth initially “ankylosed” to both the maxilla and the mandible. Treatment procedures employing a change in the cant of the occlusal plane, forward or backward rotations of the mandible, and/or surgical procedures can be superimposed on this 2-year growth estimate (Fig. 8). Whatever procedures employed, their net effect can be measured as a change in the A-Pg (OP) relationship. With Patient D. B., it can be seen that the net anticipated change in A-Pg( OP) was 2.9 mm., a result of facial growth and a forward mandibular growth rotation. No change in the cant of the occlusal plane was planned. To indicate this change in the relationship of the mandibular and maxillary denture bases on the occlusogram tracings, dots are placed 2.9 mm. anterior to the maxillary transverse registration line. Since the growth estimate for Patient 1). B. shows that the mandible is moving forward relative to the maxilla, the mandibular occlusogram tracing is slid forward along the maxillary midsagittal registration line until its transverse registration line is registered at these dots (Fig. 9). In those instances in which the growth estimate and/or treatment procedures (mandibular resections) show that the mandible moves backward relative to the maxilla, the dots indicating the magnitude of this change are placed instead on the mandibular occlusogram tracing while the maxillary occlusogram tracing is slid forward until its transverse registration line is registered on the dots. With the transverse registration line registered on the dots, the sides of the occlusogram tracings are then temporarily fixed with masking tape while the bottom edges of the tracings are cut evenly. Mylar tape may now be used to fix the adjusted occlusogram tracings permanently in a position that represents the denture base relationship at the end of the treatment (that is, 2 years). Within these newly positioned “denture bases,” the “ankylosed” teet.h may now be repositioned. In planning the dental changes for Patient D. B., it was decided that the same cant and level of the occlusal the ttt hhh t eee h e
660
Am.
Na.rcotte
Fig. 9. The mandibular lary
occlusogram
Fig. with
10. The position the
mandibular
Fig. 11. Buccal with
solid
transverse (arrows).
tracing
cusp
of the incisors. tips
registration
maxillary and
central
incisal
edges
line
is aligned
incisors of
with
(arrow)
maxillary
in ideal and
the
dots overjet
mandibular
on
J. Orthod. June 1976
the
and arches
maxiloverbite shown
lines.
Fig. 12. Contact
points
of the
arch
are
indicated
by the
dashed
lines.
The line representing the average position of the contact points is then constructed on both maxillary and mandibular occlusogram tracings. With a set of dividers, the distance from the buccal cusp tips to the contact area is measured and transferred to each corresponding occlusogram tracing. These points are then connected with a dashed line (Fig. 12) and, with both occlusogram tracings folded, one can check the correspondence of the resulting arches. The mandibular buccal cusp tips should be slightly lingual to the maxillary contact line. Determining the arch length status of these idealized arches requires a comparison of the tooth diameters to the arch length. These tooth diameters, from one second premolar around to the other second premolar, are marked off on the contact line (dashed line in Fig. 12)) starting from the treatment midline. In the determination of this treatment midline, three midlines are evaluated: the facial midline, the apical base midline, and the geometric midline.
Oc.clusogram iw treatment
pla?b?ling
661
The location of the facial midline is noted in relation to the maxillary dental midline. In Patient D. B. the facial midline (CT’-Sn-Pg’) was found to be 0.5 mm. to the left of the maxillary dental midline. This measurement is transferred to both occlusogram tracings as a dash-dot-dot arrow (Fig. 13). Conceptually, the apical base midline of the maxilla and mandible is the anatomic midline of the maxilla or mandible when viewed from the anterior. The apical base midline is considered since there is often a discrepancy between the anatomic centers of the maxilla and the mandible, with the dental midlines being skewed in similar fashion. In correcting this skeletal midline discrepancy, the anterior teeth, if they are in normal axial inclination, must be translated laterally rather than tipped. This apical base midline discrepancy, then, indicates the degree of lateral translation required of the anterior teeth. In this sense it is a limiting midline, since significant lateral translation is difficult to accomplish. In the presence of an ideal occlusion the axial inclinations of the teeth give a clue as to where the anatomic centers of the maxilla and mandible are located, that is, midway between the roots of the central incisors. To find this apical base midline in most occlusions, however, a tracing is made of the posteroanterior cephalometric head film and the maxillary and mandibular central incisors are schematically corrected to ideal axial inclinations (dotted incisors in Fig. 14). The point found midway between the roots of the corrected incisors is regarded as the apical base midline for that arch. A frontal occlusal plane is constructed by connecting two points across the arch (for example, mesiobuccal cusp tips of mandibular right and left first molars). From these apical base midlines, perpendicular lines are dropped to this frontal occlusal plane to indicate the magnitude of the maxillomandibular apical base midline discrepancy. The apical base midlines are also indicated on the occlusogram tracings with a solid-line arrow at the point where the perpendicular line contacts the original central incisors on the posteroanterior tracing. For Patient D. B., the apical base midline discrepancy between the maxilla and the mandible is 1.5 mm., measured between the two solidline arrows when the occlusogram tracings are folded (Fig. 13). The geometric midline represents the midpoint of the desired arch circumference, assuming that the ideal position of the posterior teeth is achieved. The position of the posterior teeth in both arches is thus considered, with the space posterior to these teeth and the symmetry of axial inclinations from right to left serving as guides. The geometric midline would be found at the midpoint of each ideal arch circumference. If the maxillary posterior teeth on the right side were positioned anterior to the posterior teeth on the left side, the geometric midline would be skewed to the left. To determine the geometric midline in Patient D. B., both the study casts and the right and left 45 degree cephalometric head films are used. The position of the maxillary teeth in the arch can often be detected by noting where a landmark, such as the mesial surface of the maxillary first molar, is in relation to the corresponding hamular notch. In Patient D. B., both right and left distances between the mesial surface of the maxillary first molar and the hamular notches were identical, and apparently the maxillary teeth are positioned identically relative to the posterior borders of the maxillary arch. For the mandibular arch,
662
Ma,rcotte
R
1 Fig. 13. Midlines metric midline.
are
indicated:
Fig. 14. Incisors normalized apical base midlines. Fig. 15. posterior
Right teeth.
and
left
-
l
, Facial
l
schematically 45
degree
Fig. 16. Dotted line at lower right that is required for a symmetrical movement is required.
head
midline; on
films
-,
tracing used
first molar indicates buccal occlusion.
of for
apical
base
midline:
posteroanterior assessing
the Other
slight dotted
- - - , geo-
head axial distal lines
inclinations
film
to find of
the
crown movement indicate that no
Volume Number
69 6
Occlusogram
in trea,tment
planning
663
such obvious landmarks are unavailable, but an approximation can be had by noting the amount of tooth exposed on a partially erupting second molar. If one side has a second molar nearly fully exposed and the other side has a second molar with only three quarters of its crown exposed, it might be reasonably suspected that the former side is slightly anterior to the latter. Such was the case in Patient D. B. The right second molar was exposed slightly more than the left side, and, allowing for differences in eruption times of these teeth, one might suspect that the right posterior teeth were slightly anterior to the left posterior teeth. To corroborate any evidence of anteroposterior symmetry in the posterior segments of teeth, right and left 45-degree cephalometric films are used to determine the axial inclinations of the posterior teeth (Fig. 15). If symmetry exists in axial inclinations, one would be more inclined to think that symmetry in position also exists. If the axial inclinations are asymmetrical, one side is identified as being most normal and an estimate is made of the changes in crown position that must be made on the other side for symmetrical axial inclinations. For example, in Patient D. B., the maxillary axial inclinations were found to be bilaterally symmetrical, except for the second molars (Fig. 15). Compared to the 45-degree cephalometric standards for her age group, the mandibular right first and second molars were tipped mesially. To achieve the symmetrical axial inclinations required for a symmetrical buccal occlusion, the mandibular right first and second molars must be uprighted with their crowns moving distally, as indicated by the dotted line in Fig. 16. Dividers can then be used to find the geometric center of each idealized arch circumference from the mesial surface of this first molar position around to the mesial surface of the other first molar position. With the occlusogram tracings folded, the dotted lines indicating the mesial surfaces of the first molars should be parallel to each other while the geometric midlines are at the same location for both the maxillary and mandibular occlusogram tracings. This is indicated on the occlusogram tracings with a dashed arrow (Fig. 13). From these various midlines on the occlusogram tracings, one treatment midline must be selected. The treatment midline selected for Patient D, B. was the geometric midline (dashed arrow), which is a practical midline in the sense that it allows for a symmetric occlusion. Usually, a hash mark is constructed across the arch circumference to indicate this treatment midline. The arch length status is next determined by measuring the widest mesiodistal diameters of the teeth on the dental casts and transferring these measurements to the corresponding contact line of each arch, starting from the treament midline. A small hash mark is placed to indicate the distal surface of each tooth (Fig. 17). It can be seen in Fig. 17 that if all teeth from the central incisors to the second premolars are included in the arch, the arch length inadequacy for the maxillary arch is 7.8 mm. on the right and 5.8 mm. on the left, and for the mandibular arch it is 5.5 mm. on both the right and left sides. In the case of Patient D. B., it was decided that the mandibular right and left first premolars should be extracted. Omitting these first premolars from the lower contact line (Fig.l7), each second premolar width is placed next to the canine hash mark. The arrows in Fig. 17 indicate the final position of the distal surface
664
Mascotte
Fig.
17. Tooth
Fig.
18. Occlusogram
diameters
marked
Fig.
19.
Frontal
view
before
Fig.
20.
Frontal
view
after
tracings
off on contact folded
to check
line final
showing
arch
length
status.
occlusion.
treatment. treatment.
of the second premolar or the mesial surface of the first molar, that is, the required loss of anchorage. The arch length inadequacy in the maxillary arch was also solved by extraction of the right and left first premolars. With these first premolars omitted from the maxillary contact line, the location of the mesial surface of the maxillary first molar is indicated by the arrows in Fig. 17. It can be seen that on the right
Odusogram
Fig.
21.
Maxillary
occlusal
view
before
Fig.
22.
Maxillary
occlusal
view
after
Fig.
23.
Mandibular
occlusal
view
before
Fig.
24.
Mandibular
occlusal
view
after
in treatment
plawing
665
treatment. treatment. treatment, treatment.
side the maxillary first molar cannot afford any mesial movement, while on the left side the first molar can be allowed to slip mesially 1.5 mm. With the occlusogram tracings folded (Fig. 18), it becomes possible to check the final occlusion as one would do with a diagnostic wax setup. Dots of different colors can be placed on the solid line representing the buccal cusp tips, and these dots may be seen occluding with the opposing embrasures (hash lines on opposing tracing). Discussion
To achieve the orthodontic treatment objectives, the occlusogram tracing allows the orthodontist to plan specific dental movements in the transverse plane. With the completed occlusogram tracings (Fig. 17)) it can be seen that, to achieve the initial treatment objectives, the following must occur : A. 2.9 mm. change in A-Pg(OP) B. Extraction of maxillary and mandibular C. Anteroposterior position of the teeth
first
premolar8
.4n,. J. Orth,od. June 1976
Fig.
25.
Right
Fig.
26.
Left
side
side
after
before
Fig.
27.
Left
side
before
treatment.
Fig.
28.
Right
after
treatment.
side
Mandibular
Maxillary
treatment. treatment.
arch
arch
’ 1
D.
Final
arch
Mandibular
Maxillary
Retract Protract Protract
incisors left buccal right buccal
segment segment
2.0 mm. 2.0 mm. 2.5 mm.
Retract Protract Protract
incisors right buccal left buccal
segment segment
4.8 mm. 0.0 mm. 1.5 mm.
widths
arch
arch
Intercanine Interpremolar Intermolar
width width width
27.5 34.0 41.0
mm. mm. mm.
Intercanine Interpremolar Intermolar
width width width
31.5 42.0 47.5
mm. mm. mm.
The initial (July, 1972) and final (April, graphs have been included (Figs. 19 to 28).
1974) intraoral
Kodachrome
photo-
Conclusion
A method of planning orthodontic treatment in the transverse plane has been presented. The occlusogram procedure outlined augments other orthodontic records in order to define more specifically the requirements of successful orthodontic treatment. Anchorage requirements, extractions, if any, and arch widths plus the final occlusal relationships can be determined at the outset of orthodontic treatment. Summary
A procedure for using occlusogram procedures in planning specific movements in the transverse plane has been described. Using actual patient records, specific requirements have been outlined to achieve over-all orthodontic treatment objectives. REFERENCES
1. Simon, Boston, 2. Burstone, School
Paul TV.: Fundamental principles 1926, The Stratford Company. C. J. : Personal communication. of Dental
Medicine
(06032)
of
a systematic
diagnosis
of
dental
anomalies,
R. Marcotte,
Famingto?t,
D.D.S.,
M.S.D.*
Conw
P
articularlp since the advent of radiographic cephalometrics, orthodontists have planned treatment primarily in two dimensions, although earlier leaders in the field, such as Simon1 developed three-dimensional analytical procedures. Currently, the lateral cephalometric head film is used in many respects, to the exclusion of records that define the third dimension, Methods for producing positive-print 1 :l photographs of dental casts were earlier developed by C. J. Burstone ; with tracings of these photographs (occlusograms) and proper cephalometric head films, it is now possible to make treatment discussions in all three planes of space.2 It is the purpose of this article to demonstrate the use of the occlusogram in planning orthodontic treatment and to describe the procedures in sufficient detail so that it can be used practically. Specifically, the procedures will permit the orthodontist to determine (1) the anchorage requirements, (2) the arch length status, (3) the final arch widths, (4) the teeth to be removed, if any, and (5) the final occlusal relationships. Occlusogram
procedure
The records of Patient I). B., a Caucasian girl with a developmental age of 11 years 6 months, will be used to illustrate the procedures. The occlusogram procedure requires accurate positive-print photographs of the occlusal aspects of oriented dental casts. The dental impressions are made in the usual manner, and the resulting casts must be trimmed according to the following specifications : The posterior borders of the dental casts are trimmed perpendicular to the occlusal plane (Fig. 1). Since the centric relation position of the dental casts will be used as a reference position, the posterior borders of the casts must be made flush with each other when the casts are in the. centric relation position. This reference position requires that the wax jaw registration be made with the mandible in *Assistant Medicine.
Professor
of
Orthodontics,
University
of
Connecticut
School
of
Dental
655
656
Fig.
Awl.
Maqrcotte
1. The
posterior
borders
Fig.
2.
Fig.
3. The
Registration
Fig.
4. A 1: 1 positive-print
occlusogram
of the
grooves
are
camera film
dental
casts
placed
assembly of the
in for
occlusal
are the
perpendicular posterior
producing aspects
to the surfaces
occlusal of
1 :l positive-print of the dental
the
J. Orthod. June 1976
plane. dental
casts.
films. casts.
its most retruded position and that the wax registration recording the occlusal surfaces of the teeth be made without perforating the wax. This wax centric relation registration is then placed between the dental casts while the posterior borders of the casts are trimmed. Viewed from the occlusal aspect, the posterior borders of the casts are also perpendicular to the palatal midline and, for lateral orientation, each cast will have an extended registration groove (Fig. 2). This registration groove is placed in the backs of both casts simultaneously by means of a custom-made dental cast scriber. The casts have thus been trimmed with their backs mutually perpendicular to the occlusal plane and to the palatal midline and have also been scribed to permit the positive-print occlusograms to be oriented laterally. The casts are then finished and polished in the usual manner.
0cclusogra.m
in treatment
planning
6S7
To make standard photographs of the occlusal aspects of the dental casts, the occlusogram camera assembly consists of a 4 by 5 inch box camera, a dental cast stage, two 375watt floodlights, and a hinged Plexiglas plate (Fig. 3). The camera is mounted on a sliding track, so that the distance from the edge of the stage can be adjusted and fixed to produce a 1 :l magnification. For this particular installation, a 210 mm. lens is found to be satisfactory. The dental cast stage has an adjustable guide onto which fit the registration grooves on the backs of the dental casts. Each dental cast is placed on this stage guide and is brought up to the leading edge of the stage. Since the camera has been focused on this leading edge, the occlusal aspects of the dental cast are in focus at a 1 :l magnification. Registration dots which are located in the leading edge of the stage will also be recorded on the occlusogram. With a fine-grain positive film placed into the film cassette, and with both floodlights focused on the dental cast, a typical exposure of 4 seconds at f45 is made. Processed according to manufacturer’s directions, maxillary and mandibular occlusograms are produced at 1 :l magnification (Fig. 4). Using the registration dots on the leading edge of the stage as reference points, both occlusograms are registered on these dots and permanently fixed at the bottom edge with a noncracking type of tape (for example, Mylar tape). Since the positive-print film is transparent, the existing occlusal relationships in centric relation can be seen when the occlusograms are folded over. For most treatment procedures, however, an occlusogram tracing is required. For this occlusogram tracing, acetate paper is placed over the occlusograms and the maxillary and mandibular teeth are outlined, showing the gingival tooth contours, incisal edges, buccal cusp ridges, central grooves, and cusp tips. Also traced are the palatal rugae, the midpalatal raphe, the fovea palatinus, and the registration dots (Fig. 5). Application
to orthodontic
treatment
planning
In order to orient the occlusogram tracings, midsagittal and transverse‘registration lines are constructed. The maxillary midsaggittal registration line is constructed by connecting the midpoints of the incisive papilla, the midpalatal raphe, and the fovea palatinus (Fig. 6). The maxillary transverse registration line is constructed distal to the last molar in the arch and perpendicular to the midsagittal registration line. The maxillary and mandibular occlusogram tracings are then separated by cutting the acetate paper midway between both tracings. The occlusogram tracings are assembled, using the registration dots, and the maxillary registration lines are duplicated on the mandibular occlusogram tracing (Fig. 7). Both pieces of tracing paper, when oriented as in Fig. 7, can be thought of as the maxillary and mandibular denture bases in centric relation at the beginning of orthodontic treatment. Since the anteroposterior position of the denture bases is influenced by growth, facial growth rotations, changes in the cant of the occlusal plane, and/or surgery, these positions should be anticipated for the period of treatment and incorporated into the occlusogram tracings.
AWL J. Orthod. June 1976
. .
I
*-
D.8 11.6 ~WWS-solid line 13.6 years--dashed lme Net change
in A- Pg (OP):2,9m
Denrcfoctal Trerxtmmt Obtecrivan--dotted line
Fig.
5. Occlusogram
Fig. 6. The maxillary raphe, and the fovea Fig. 7. Both registration Fig.
tracing. midsagittal palatinus.
occlusogram tracings lines are transferred
8. Dentofacial
objectives
line
connecting
are assembled to the mandibular
diagrammed
the
incisive
papilla,
on the registration dots, occlusogram tracing.
on a 2-year
growth
estimate.
the and
midpalatal the
maxillary
From the initial tracing of Patient I). B.‘s cephalometric head film, a. “-year growth estimate is made with the teeth initially “ankylosed” to both the maxilla and the mandible. Treatment procedures employing a change in the cant of the occlusal plane, forward or backward rotations of the mandible, and/or surgical procedures can be superimposed on this 2-year growth estimate (Fig. 8). Whatever procedures employed, their net effect can be measured as a change in the A-Pg (OP) relationship. With Patient D. B., it can be seen that the net anticipated change in A-Pg( OP) was 2.9 mm., a result of facial growth and a forward mandibular growth rotation. No change in the cant of the occlusal plane was planned. To indicate this change in the relationship of the mandibular and maxillary denture bases on the occlusogram tracings, dots are placed 2.9 mm. anterior to the maxillary transverse registration line. Since the growth estimate for Patient 1). B. shows that the mandible is moving forward relative to the maxilla, the mandibular occlusogram tracing is slid forward along the maxillary midsagittal registration line until its transverse registration line is registered at these dots (Fig. 9). In those instances in which the growth estimate and/or treatment procedures (mandibular resections) show that the mandible moves backward relative to the maxilla, the dots indicating the magnitude of this change are placed instead on the mandibular occlusogram tracing while the maxillary occlusogram tracing is slid forward until its transverse registration line is registered on the dots. With the transverse registration line registered on the dots, the sides of the occlusogram tracings are then temporarily fixed with masking tape while the bottom edges of the tracings are cut evenly. Mylar tape may now be used to fix the adjusted occlusogram tracings permanently in a position that represents the denture base relationship at the end of the treatment (that is, 2 years). Within these newly positioned “denture bases,” the “ankylosed” teet.h may now be repositioned. In planning the dental changes for Patient D. B., it was decided that the same cant and level of the occlusal the ttt hhh t eee h e
660
Am.
Na.rcotte
Fig. 9. The mandibular lary
occlusogram
Fig. with
10. The position the
mandibular
Fig. 11. Buccal with
solid
transverse (arrows).
tracing
cusp
of the incisors. tips
registration
maxillary and
central
incisal
edges
line
is aligned
incisors of
with
(arrow)
maxillary
in ideal and
the
dots overjet
mandibular
on
J. Orthod. June 1976
the
and arches
maxiloverbite shown
lines.
Fig. 12. Contact
points
of the
arch
are
indicated
by the
dashed
lines.
The line representing the average position of the contact points is then constructed on both maxillary and mandibular occlusogram tracings. With a set of dividers, the distance from the buccal cusp tips to the contact area is measured and transferred to each corresponding occlusogram tracing. These points are then connected with a dashed line (Fig. 12) and, with both occlusogram tracings folded, one can check the correspondence of the resulting arches. The mandibular buccal cusp tips should be slightly lingual to the maxillary contact line. Determining the arch length status of these idealized arches requires a comparison of the tooth diameters to the arch length. These tooth diameters, from one second premolar around to the other second premolar, are marked off on the contact line (dashed line in Fig. 12)) starting from the treatment midline. In the determination of this treatment midline, three midlines are evaluated: the facial midline, the apical base midline, and the geometric midline.
Oc.clusogram iw treatment
pla?b?ling
661
The location of the facial midline is noted in relation to the maxillary dental midline. In Patient D. B. the facial midline (CT’-Sn-Pg’) was found to be 0.5 mm. to the left of the maxillary dental midline. This measurement is transferred to both occlusogram tracings as a dash-dot-dot arrow (Fig. 13). Conceptually, the apical base midline of the maxilla and mandible is the anatomic midline of the maxilla or mandible when viewed from the anterior. The apical base midline is considered since there is often a discrepancy between the anatomic centers of the maxilla and the mandible, with the dental midlines being skewed in similar fashion. In correcting this skeletal midline discrepancy, the anterior teeth, if they are in normal axial inclination, must be translated laterally rather than tipped. This apical base midline discrepancy, then, indicates the degree of lateral translation required of the anterior teeth. In this sense it is a limiting midline, since significant lateral translation is difficult to accomplish. In the presence of an ideal occlusion the axial inclinations of the teeth give a clue as to where the anatomic centers of the maxilla and mandible are located, that is, midway between the roots of the central incisors. To find this apical base midline in most occlusions, however, a tracing is made of the posteroanterior cephalometric head film and the maxillary and mandibular central incisors are schematically corrected to ideal axial inclinations (dotted incisors in Fig. 14). The point found midway between the roots of the corrected incisors is regarded as the apical base midline for that arch. A frontal occlusal plane is constructed by connecting two points across the arch (for example, mesiobuccal cusp tips of mandibular right and left first molars). From these apical base midlines, perpendicular lines are dropped to this frontal occlusal plane to indicate the magnitude of the maxillomandibular apical base midline discrepancy. The apical base midlines are also indicated on the occlusogram tracings with a solid-line arrow at the point where the perpendicular line contacts the original central incisors on the posteroanterior tracing. For Patient D. B., the apical base midline discrepancy between the maxilla and the mandible is 1.5 mm., measured between the two solidline arrows when the occlusogram tracings are folded (Fig. 13). The geometric midline represents the midpoint of the desired arch circumference, assuming that the ideal position of the posterior teeth is achieved. The position of the posterior teeth in both arches is thus considered, with the space posterior to these teeth and the symmetry of axial inclinations from right to left serving as guides. The geometric midline would be found at the midpoint of each ideal arch circumference. If the maxillary posterior teeth on the right side were positioned anterior to the posterior teeth on the left side, the geometric midline would be skewed to the left. To determine the geometric midline in Patient D. B., both the study casts and the right and left 45 degree cephalometric head films are used. The position of the maxillary teeth in the arch can often be detected by noting where a landmark, such as the mesial surface of the maxillary first molar, is in relation to the corresponding hamular notch. In Patient D. B., both right and left distances between the mesial surface of the maxillary first molar and the hamular notches were identical, and apparently the maxillary teeth are positioned identically relative to the posterior borders of the maxillary arch. For the mandibular arch,
662
Ma,rcotte
R
1 Fig. 13. Midlines metric midline.
are
indicated:
Fig. 14. Incisors normalized apical base midlines. Fig. 15. posterior
Right teeth.
and
left
-
l
, Facial
l
schematically 45
degree
Fig. 16. Dotted line at lower right that is required for a symmetrical movement is required.
head
midline; on
films
-,
tracing used
first molar indicates buccal occlusion.
of for
apical
base
midline:
posteroanterior assessing
the Other
slight dotted
- - - , geo-
head axial distal lines
inclinations
film
to find of
the
crown movement indicate that no
Volume Number
69 6
Occlusogram
in trea,tment
planning
663
such obvious landmarks are unavailable, but an approximation can be had by noting the amount of tooth exposed on a partially erupting second molar. If one side has a second molar nearly fully exposed and the other side has a second molar with only three quarters of its crown exposed, it might be reasonably suspected that the former side is slightly anterior to the latter. Such was the case in Patient D. B. The right second molar was exposed slightly more than the left side, and, allowing for differences in eruption times of these teeth, one might suspect that the right posterior teeth were slightly anterior to the left posterior teeth. To corroborate any evidence of anteroposterior symmetry in the posterior segments of teeth, right and left 45-degree cephalometric films are used to determine the axial inclinations of the posterior teeth (Fig. 15). If symmetry exists in axial inclinations, one would be more inclined to think that symmetry in position also exists. If the axial inclinations are asymmetrical, one side is identified as being most normal and an estimate is made of the changes in crown position that must be made on the other side for symmetrical axial inclinations. For example, in Patient D. B., the maxillary axial inclinations were found to be bilaterally symmetrical, except for the second molars (Fig. 15). Compared to the 45-degree cephalometric standards for her age group, the mandibular right first and second molars were tipped mesially. To achieve the symmetrical axial inclinations required for a symmetrical buccal occlusion, the mandibular right first and second molars must be uprighted with their crowns moving distally, as indicated by the dotted line in Fig. 16. Dividers can then be used to find the geometric center of each idealized arch circumference from the mesial surface of this first molar position around to the mesial surface of the other first molar position. With the occlusogram tracings folded, the dotted lines indicating the mesial surfaces of the first molars should be parallel to each other while the geometric midlines are at the same location for both the maxillary and mandibular occlusogram tracings. This is indicated on the occlusogram tracings with a dashed arrow (Fig. 13). From these various midlines on the occlusogram tracings, one treatment midline must be selected. The treatment midline selected for Patient D, B. was the geometric midline (dashed arrow), which is a practical midline in the sense that it allows for a symmetric occlusion. Usually, a hash mark is constructed across the arch circumference to indicate this treatment midline. The arch length status is next determined by measuring the widest mesiodistal diameters of the teeth on the dental casts and transferring these measurements to the corresponding contact line of each arch, starting from the treament midline. A small hash mark is placed to indicate the distal surface of each tooth (Fig. 17). It can be seen in Fig. 17 that if all teeth from the central incisors to the second premolars are included in the arch, the arch length inadequacy for the maxillary arch is 7.8 mm. on the right and 5.8 mm. on the left, and for the mandibular arch it is 5.5 mm. on both the right and left sides. In the case of Patient D. B., it was decided that the mandibular right and left first premolars should be extracted. Omitting these first premolars from the lower contact line (Fig.l7), each second premolar width is placed next to the canine hash mark. The arrows in Fig. 17 indicate the final position of the distal surface
664
Mascotte
Fig.
17. Tooth
Fig.
18. Occlusogram
diameters
marked
Fig.
19.
Frontal
view
before
Fig.
20.
Frontal
view
after
tracings
off on contact folded
to check
line final
showing
arch
length
status.
occlusion.
treatment. treatment.
of the second premolar or the mesial surface of the first molar, that is, the required loss of anchorage. The arch length inadequacy in the maxillary arch was also solved by extraction of the right and left first premolars. With these first premolars omitted from the maxillary contact line, the location of the mesial surface of the maxillary first molar is indicated by the arrows in Fig. 17. It can be seen that on the right
Odusogram
Fig.
21.
Maxillary
occlusal
view
before
Fig.
22.
Maxillary
occlusal
view
after
Fig.
23.
Mandibular
occlusal
view
before
Fig.
24.
Mandibular
occlusal
view
after
in treatment
plawing
665
treatment. treatment. treatment, treatment.
side the maxillary first molar cannot afford any mesial movement, while on the left side the first molar can be allowed to slip mesially 1.5 mm. With the occlusogram tracings folded (Fig. 18), it becomes possible to check the final occlusion as one would do with a diagnostic wax setup. Dots of different colors can be placed on the solid line representing the buccal cusp tips, and these dots may be seen occluding with the opposing embrasures (hash lines on opposing tracing). Discussion
To achieve the orthodontic treatment objectives, the occlusogram tracing allows the orthodontist to plan specific dental movements in the transverse plane. With the completed occlusogram tracings (Fig. 17)) it can be seen that, to achieve the initial treatment objectives, the following must occur : A. 2.9 mm. change in A-Pg(OP) B. Extraction of maxillary and mandibular C. Anteroposterior position of the teeth
first
premolar8
.4n,. J. Orth,od. June 1976
Fig.
25.
Right
Fig.
26.
Left
side
side
after
before
Fig.
27.
Left
side
before
treatment.
Fig.
28.
Right
after
treatment.
side
Mandibular
Maxillary
treatment. treatment.
arch
arch
’ 1
D.
Final
arch
Mandibular
Maxillary
Retract Protract Protract
incisors left buccal right buccal
segment segment
2.0 mm. 2.0 mm. 2.5 mm.
Retract Protract Protract
incisors right buccal left buccal
segment segment
4.8 mm. 0.0 mm. 1.5 mm.
widths
arch
arch
Intercanine Interpremolar Intermolar
width width width
27.5 34.0 41.0
mm. mm. mm.
Intercanine Interpremolar Intermolar
width width width
31.5 42.0 47.5
mm. mm. mm.
The initial (July, 1972) and final (April, graphs have been included (Figs. 19 to 28).
1974) intraoral
Kodachrome
photo-
Conclusion
A method of planning orthodontic treatment in the transverse plane has been presented. The occlusogram procedure outlined augments other orthodontic records in order to define more specifically the requirements of successful orthodontic treatment. Anchorage requirements, extractions, if any, and arch widths plus the final occlusal relationships can be determined at the outset of orthodontic treatment. Summary
A procedure for using occlusogram procedures in planning specific movements in the transverse plane has been described. Using actual patient records, specific requirements have been outlined to achieve over-all orthodontic treatment objectives. REFERENCES
1. Simon, Boston, 2. Burstone, School
Paul TV.: Fundamental principles 1926, The Stratford Company. C. J. : Personal communication. of Dental
Medicine
(06032)
of
a systematic
diagnosis
of
dental
anomalies,
